US2120381A - Materials testing apparatus - Google Patents

Description

June 14, 1938. TRQXELL, 2,120,381

MATERIALS TESTING APPARATUS Filed Oct. 9, 1935 2 Sheets-Sheet l as v INVENTOR June 14, 1938. G. E. TROXELL MATERIALS TESTING APPARATUS 1935 2 Sheets-Sheet 2 Filed Oct. 9

INVENTOR 6. E. Trox y fl n 1 ATORN Y v Patented June 14, 1938 UNITED 'f STATES PATENT- OFFICE Baldwin- Southwark Corporation, a

tion of Delaware corpora- I Application October 9,1935, Serial No.'44 ,23,3 1 Claims. (01. 265-14 This invention relates generally to an improved apparatus for controlling or regulating pressure or load or for controlling the application of power to a movable member which may serve various purposes, one of which as specifically shown herein is to load a specimen in a materials testing machine although certain principles and features of the invention are broadly applicable to various devices which may be either foreign or auxiliary to materials testing machines and in.

which pressure or load is broadly a factor.

It is one object of my invention to provide an improved sensitive apparatus for efi'ectively controlling or regulating pressure, load or the application of power to a power driven movable memher. In one specific aspect of the invention I have applied one form of the apparatus, to the control of a materials testing machine so as to maintain a substantially constant load on a specimen and maintain such load within relatively narrow limits at any selected value of the load range or to change the load at any desired rate. It will be understood that precision qualities and sensitiveness are vital to apparatus of any kind 25 which involves means responsive to the load of a specimen and that it is always desirable that the initial load responsive elements of such apparatus ,shall be as free as possible from friction or restraint. Any inaccuracies that may be present in 30 the initial load responsive elements will be immediately reflected in a very much magnified manner in the power movable member which it is desired to control. object of my invention to accomplish this initial 35 load responsiveness with a great deal of sensitivity and accuracy and to precisely control a larger source of power.

. In a hydraulic materials testing machine a source of hydraulic power is supplied to a load 40 producing cylinder and ram for stressing a specimen. Due to leakage between the ram and cylinder or other possible causes, considerable difliculty may be experienced in maintaining constant load on the specimen especially for an 46 appreciable period of time.

In one specific application of my invention as herein disclosed I employ a hydraulically operated load responsive member, such as an indicating hand. The load responsive fiuid may be 60 taken either directly from the ram cylinder of a hydraulic type machine, or in the case of the Emery type materials testing machine the fluid may be taken from an independent weighing system which is a characteristic of the Emery type 55 machine, or in the case of mechanically operated Hence it is a further specific specimen. I then place in eflective cooperative relation to such a load responsive member, light sources and photoelectric cells arranged to control application of power to a movable member which for purposes of illustration herein is a ram of a materials testing machine but which might be a movable power driven member of any auxiliary apparatus: used in connection with a materials testing machine and necessitating that the application of power be controlled in accordance with specimen load.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a diagram of the circuits and control elements in my improved combination; L

Fig. 2 is a front elevation of the apparatus for establishing the limits within which load may be maintained;

Fig. 3 is a substantially vertical section taken on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged perspective of one of the light slots;

Fig. 5 is a diagrammatic outline of a materials testing machine to which my invention is applied for purposes of illustration.

The particular embodiment of the invention as shown herein is merely for the purpose of illustrating certain principles of the invention together with its application to one type and form of apparatus among possible others. To this end,

I have disclosed in Fig. 5 a diagrammatic out-' line of an Emery type materials testing machine wherein a specimen I is suitably supported for movable power driven member or means of any suitable form is shown specifically herein for purposes of illustration as a ram 8 This power driven means is arranged to move platen 3 upwardly to impose a compression load on the specimen, whereas in a tension test the specimen is supported by suitable grips between crosshead 2 and an upper loading crosshead 3a. A motordriven pump 3 preferably of the adjustable Hele- Shaw type supplies pressure fluid power to cylinder 3 through a pipe ill. Suitable means, provided for establishing the degree of available power, is specifically shown as a manually adjustable discharge valve Ina although the Hele- Shaw pump can also be adjusted to determine the available power. Mechanism for controlling the application of power to the movable member is specifically shown herein as comprising a spring closed relief valve I2 adapted to by-pass fluid from pipe Hi to a pump sump. Hence by suitably controlling the said power through operation of said control mechanism, it is possible to control movement of member 3 and specifically to maintain a predetermined load on a specimen. The load on the specimen is transmitted through the sensitive frame of the machine to the hydraulic support I in which fluid pressure proportional to the load is created and transmitted through a pipe 13 to a Bourdon tube generally indicated at IS in Fig. 3. The Bourdon tube as shown in Fig. 3 rotates a shaftlfi and a double end hand ll, the tube and hand broadly constituting means responsive to the load on the specimen.

Hand I1 is' placed in front of an opaque disc 13 which is preferably supported at its circular edge by a series of rollers l3 to permit angular adjustment about the axis of shaft l3. A light slot 23 is formed at one portion of disc 13. To insure a relatively narrow beam of light through said slot together with circumferential or angular adjustment thereof, there is provided a relatively thick light ray guide 2| having, as shown in Fig. 4, circumferentially elongated holes 22 to receive screws adapted for threaded engagement with disc l8. The elongated holes 22 permit angular adjustment of the light slot to assist in establishing one limit within which load is maintained. The load responsive hand I! is of sumcient width as to be able to cover slot 23 and thus intercept light from a suitable source such as an incandescent bulb 23 supported in alignment with light slot 23. Bulb 23 is enclosed within a suitable opaque casing 24 which is secured in any suitable manner to the front of disc i3 so as to move therewith during adjustment thereof. A bracket 23, for supporting a photoelectric cell 25 in alignment with the light slot,

' is secured to the rear of disc l3. Thus it is seen that the photoelectric cell 25, light ray slot 23, sourceof light 23 and disc 18 will always be maintained in fixed relation with respect to each other so as to be adjustable as a unit.

There is also provided another light ray guide 21, source of light 23 and photoelectric cell 23 to establish the other load limit. The two slots 20 and 21 are very nearly on the same diametral line, the actual offset from the diameter being adjustable due to elongated screw holes 22. For safety purposes, a guide 30, alight source 3| and a photoelectric cell 32 are substantially offset from the slot 21. It will be understood that the construction and arrangement of all of the foregoing light sources, light .guides and photoelectric cells have the same unitary relation to disc l3 and are identical to the specific construction described in connection with light 23, guide 2i and photoelectric cell 25 together with the supporting structure therefor so that the whole is adjustable as a unit.

In describing the mode of operation of the circuits and apparatus as used in controlling a and connection to the hydraulic support.

materials testing machine in response to load on a specimen for the purpose of maintaining a constant load thereon, the low, high and safety limit; light vcontrol units are respectively indicated by the numerals I, II and III. To load the specimen, pump 3 is started by closure of a switch in a pump motor circuit, the contacts of a solenoid switch 36 in this circuit being normally closed. In the circuit of said solenoid the contacts of a solenoid switch 31 are normally closed but said circuit is open by virtue of a line switch 33 being open thus permitting solenoid switch 33 to be closed and cause operation of pump 3 which thereupon supplies pressure fluid to ram cylinder 6. During this time by-pass valve [2 is closed so that by adjusting the degree of opening of valve 10a or by'adjusting the stroke of pump 9, sufficient fluid is pumped to load the specimen. When the desired load is reached, then valve Illa is adjusted to reduce flow therethrough to the point where it just maintains a constant load on the specimen. The specimen load is indicated on the usual load indicating dial 33 which, as shown in said Emery patent, has its own Bourdon tube This Bourdon tube is separate from tube I5 and hand ll. During the foregoing loading period, Bourdon tube I5' and hand I! will have moved in accordance with the load. When the desired load is reached, the disc l3 of the load maintainer apparatus is rotated manually in a clockwise direction (Fig; 2) through any suitable means such .as a handwheel 34, a shaft 35 and a bevel gear 36. Gear 36 drives one of rollers l3 which is preferably a gear meshing with peripheral gear teeth on disc l3 to rotate the same. The rotation of disc I8 is continued until one end of,hand I] of the load maintainer has relatively passed light control unit III but before said end of the hand has reached light unit II. This position of hand I1 is diagrammatically indicated in dotted lines at 33', Fig. 1. Switches 38, 33 and 43 are then substantially simultaneously closed with the result that current from a main line 4| is supplied through switch 38 to energize a transformer 42. The secondary circuit of this transformer supplies current to light sources 23, 23 and 3|. Flow of light through light guide 33 will permit cell 32 to cause energization of the solenoid ofswitch 31 as from a battery 43. Contacts of switch 31 will thereupon open, thus preventing energization of the solenoid of switch 33 at the time of closure of switch 33. Hence the contacts of switch 36 will remain closed to permit the pump to continue operation. Light also flows through guide 21 to permit cell 23 to cause energization of a solenoid of a switch 44, the circuit therefor being from battery 43 through a wire 45, cell 29, a wire 43, solenoid of switch 44, and a wire 41 to the other side of battery 43. Simultaneously, flow of light through guide 23 upon cell 25 establishes a circuit from battery 43 through wire 45 cell 25 to a solenoid of a solenoid switch 43 and thence through wire 41 to the other side of the battery. Energization of the solenoids of switches 44 and 43 causes the same to open and close respectively. The energization of the foregoing solenoids merely places the control circuits in an initial operative condition. In order to establish the lower limit above which it is desired to maintain load on the specimen, the operator continues clockwise rotation of disc I3, Fig. 2. During this rotation, hand I! will first intercept light through guide 21, thereby deenergizing solenoid of switch 44 and permitting its contacts to complete a circuit for a solenoid II as by wires 49 and 52. Energization of solenoid 5| causes closure of contacts 53 thereby estab-l, lishing a circuit for solenoid 54, through a wire 56, to open by-pass valve l2. While opening of this valve will immediately cause a decrease of load, yet the amount of fluid by-passed is so small that the rate of decrease of load is sufficiently low as to permit continued rotation of disc it until it just intercepts the low limit light guide and thereby-immediately recloses the by-passvalve with consequent increase of load on the specimen. The foregoing reestablished circuit is as follows: When light guide 2|! is Just covered, cell and the solenoid of switch 48 are deenergized to permitits contacts to open thereby deenergizing solenoid 5| and opening contacts 53. Solenoid 54 is thereby deenergized and valve l2 closed by gravity or by fluid pressure, and hence the pump increases the load on the specimen.

.As the load increases on the specimen, hand I1 ,will move in a clockwise direction as viewed in Fig 2, this direction being diagrammatically indicated by arrow A in Fig. l. The hand thus moves away from the light guide 20 and toward guide 21 with the result that the light beam through guide 20 energizes cell 25 to cause energization of the solenoid of switch 46, thereby reclosing its contacts but without establishing any circuit. As the load continues to increase on the specimen, hand |1 will ultimately intercept the beam of light through guide 21 and thus deenergizes cell 29 and the solenoid of switch 44. The contacts of switch 44 thereupon fall to. their closed position and establish a circuit from one side of main line 4| through switch 39, solenoid 5|, across contacts of solenoid switch 48 (which were closed when hand l1 uncovered guide 20), wires 49 and 52, across the closed contacts of solenoid switch 44 to the other side of the main line 4|. Energization of solenoid 5| closes contacts 53 and also closes a contact 50. Thereupon solenoid 54 is energized to open by-pass valve l2. A portion of the pressure fluid from the pump is thus by-passed so that load on the specimen will decrease, if at-all, but in any event will not increase. Any decrease in the application of load on the specimen will depend usually upon the leakage between the ram and cylinder and upon the adjustment of the pump or its, discharge valve Illa. However, assuming that for anyone of various causes, the load on the specimen decreases, then load responsive hand |1 will move away from light guide 21 toward guide 20. When the beam of light thus energizes cell 29, the solenoid of switch 44 is reenergized to open its contacts. However, the by-pass valve l2 will continue to be held open due to the fact that contact 50 was'closed upon energization of solenoid 5|. The holding circuit for solenoid 5| is now through switch 39, solenoid 5|, across contacts of solenoid switch 48, wire 49, contact 50 to contacts 53 and wire 56 to the other side of the supply line. Thus solenoid 54 is maintained energized so that by-pass valve I2 is in open position to permit the continued decrease in load on the specimen. Hand l1, moving in the direction of guide 20 as the load decreases, will again intercept the light therethroughso as to cause closure of the by-pass valve in the manner previously described. 'Ihe cycle of control between the lower and upper limits 20 and 21 respectively is thereby established and this will be maintained within extremely close limits depending upon the /distance 11km guides 20 and n a. offset from a diametral line.

If for any reason the by-pass valve should not open when the light through the upper limit switch 38, thus causing the contacts of solenoid switch 38 to open and break the pump motor circuit to discontinue operation of the pump.

To indicate when the by-pass valve is open-or closed, there is provided, Fig. 1', a pair of indicating lamps 60 :and Cl whose circuits are controlled by solenoid 54 through contacts 52 movable with the solenoid core.

From the foregoing disclosure it is seen that the regulation of pressure or load or the application of power to a movable member is controlled automatically in accordance with the pressure or load and that this control is effected without imposing any friction or restraint what soever upon the load responsive means which specifically is the Bourdon tube I5 and hand l1. It is also seen that the power operated member in the form of the hydraulic ram is made to follow the load control responsive operations with a high degree of precision and with complete flexibility throughout the full load range of the apparatus regardless of other variable factors which may occur.

To change the pressure or load at any desired rate, the disc ll may be rotated, at that rate through the shaft and gearing l9 and 35.

It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. In combination, means responsive to load on a specimen stressed in a materials testing machine, a power driven member, mechanism for controlling the application of power to said member, a plurality of photoelectric cells and light beam sources therefor whose beams are adapted to be alternatively intercepted by said load responsive means upon occurrence of predetermined loads, and means whereby said cells are adapted to control said mechanism within the limits of said predetermined loads.

2. In combination, a materials testing machine having hydraulic load producing means for stressing a specimen, means for controlling the application of power to said load producing means, high and low load limit devices for controlling said power application, and means responsive to the load on a'specimen for controlling said high and low limit load-devices thereby to maintain load on a specimen within the limits set by said devices.

3. The combination set forth in claim 2 further characterized by the provision of means for setting said devices to operate at any selected a light beam source and a photoelectric cell of its own, and means responsive to the load on a specimen for controlling one or the other of the limits any increase of load on the specimen and I control of the other beam causes an increase of load on the specimen, thereby causing the load on the specimen to be maintained within the limits set by said light sources.

5. The combination set forth in claim 4 further characterized by the provision oi a safety circuit having a photoelectric cell and a light beam source therefor whose beam is adapted to be controlled to render the load producing means inoperative upon occurrence of a load in excess of a desired upper load limit.

6. A load control apparatus for a materials testing machine in which a specimen is stressed comprising, in combination, a plurality of photoelectric cells and light beam sources, means for rotatably supporting said cells and sources as a unit in fixed relative relation to each other, and

a member freely movable between said cells and their light sources so as to intercept one or the other beams thereoi automatically in accordance with load on the specimen, said intercepting member being movable about the axis 01' rotation of said unitary structure.

7. In combination, a materials testing machine having hydraulic load producing apparatus, a source or hydraulic power therefor, means whereby the load on a specimen may be brought up to a substantially predetermined value, a relief valve

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